A braking device is used in a height adjustment mechanism for a car seat; such a braking device may be configured such that an output shaft rotates by the manipulation of a lever that is provided at an input-side and designed to be swung upward or downward but the output shaft does not rotate even when a force for lowering the seat due to weights of the seat and an occupant is applied to the output shaft (see, for example, Japanese Translation of PCT International Application, Publication No. 2002-511035).
This braking device includes an outer race having a cylindrical inner peripheral surface, a plurality of brake cams (clamping members) located opposite the inner peripheral surface, and an output-side rotating member (bolt with a wing) disposed inward of the brake cams. A rotating force imparted to the brake cams is transmitted from the brake cams to the output-side rotating member; however, even though a rotating force is imparted to the output-side rotating member, the brake cams do not rotate because forces applied to the brake cams by the output-side rotating member abutting on the brake cams act mainly as forces for pressing the brake cams against the outer race and the rotating force applied from the output-side rotating member to the brake cams does not overcome the frictional forces which could be generated between the brake cams and the outer race.